Resonant Tunneling Diodes High-Speed Terahertz Wireless Communications - A Review

Resonant tunneling diode (RTD) technology is emerging as one of the promising semiconductor-based solid-state technologies for terahertz (THz) wireless communications. This article provides a review of the state of the art, with a focus on the THz RTD oscillator, which is the key component of RTD-based THz transmitters and coherent receivers. A brief summary on the device principle of operation, technology, modeling, as well as an overview of oscillator design and implementation approaches for THz emitters, is provided. A new insight to device evaluation and to the reported oscillator performance levels is also given, together with brief remarks on RTD-based THz detectors. Thereafter, an overview of the reported wireless links which utilize an RTD in either transmission or reception, or in both roles, is given. Highlight results include the record single-channel wireless data rate of 56 Gb/s employing an all RTD-based transceiver, which demonstrates the potential of the technology for future short-range communications. The article concludes with a discussion of the current technical challenges and possible strategies for future progress.

I. Introduction

For the last two decades, we have witnessed an extraordinarily fast evolution of mobile cellular networks, starting from first generation (1G) to fourth generation (4G), and with the fifth generation (5G) of wireless communication networks now being deployed [1]. Indeed, the tremendous increase in mobile data traffic and wireless networks widespread diffusion is facing the unceasing demand for ultra-broadband multigigabit wireless communication technology, capable of extremely large channel bandwidths and ultrahigh data rates required by modern multimedia services [2], including the Internet of Things [3]. This is in line with Edholm’s law [4], which states that the demand for bandwidth performance in wireless short-range communications has doubled every 18 months since 1980 [5], and so data rates of tens of gigabits per second (Gb/s) [6] had to be accommodated since around 2020 onwards [7], while hundreds of Gb/s [8] and even terabits per second (Tb/s) wireless communication links are expected within the next ten years [9], in what will be the sixth generation (6G) networks [10]. In order to meet these performance levels, an increase in the bandwidth by several tens of gigahertz (GHz) is required [11]. However, this can be achieved only through the exploitation of higher frequency spectrum regions, specifically the terahertz (THz) band [12].